According to The Sun, the 34-year-old sister of the Duchess of Cambridge and her financier husband, James, 42, are said to be delighted at the prospect of becoming parents.
The publication states that Pippa told close family and friends last week after her 12-week scan.
The Duchess of Cambridge "could not have been more delighted" after learning younger sister Pippa was pregnant, a friend revealed.
It is believed that the baby is due in October.
The Sun also reveals that Kate was the first person after Pippa’s husband, to hear the exciting news.
A friend said: “When Pippa found out she was pregnant, she was obviously thrilled and utterly overjoyed.
“Naturally, big sister Kate and parents, Carole and Michael, were the first people she told — James aside — and they could not have been more delighted.
“It’s been a tough few weeks for the two families, so this has provided some much-needed happiness and light relief.”
Earlier this month, James’ 74-year-old father, David, was accused of raping a minor.
Pippa is said to have been extremely keen to start a family following her wedding to James last May.
They have made the most of their first few months of marriage and felt the time was right to expand their family.”